20th September 2019 By Daana 0

Dodder is a dangerous neighbor Part 1

The species of dodder includes the most dangerous for cultivated plants flowering parasitic plants, combining great vitality with high fecundity. The dodger comes from tropical America and Africa, from where it spread north and south, gradually adapting to new conditions and plants and isolating new species (up to 100 species are described). There are thin and thick stalked forms.

In our country, there are more than 30 species of dodder. All of them are objects of internal quarantine. The most common and harmful: Dodder field ( Cuscuta campestris ), Dodder clover ( Cuscuta trifolii ), Dodder hmelevidnaya ( Cuscuta lupuliformis ), Dodder linen ( Cuscuta epilinum ), Dodder korotkotsvetkovaya peppermint ( Cuscuta breviflora ), Dodder Lehmann (Cuscuta lehmaniana).

Dodgers are aerial parasites whose body has turned into a filiform or cord-like, curly, yellowish, greenish-yellow or reddish smooth or warty, chlorophyll-free stalk with barely visible traces of leaves in the form of scales. Plants are devoid of roots, feed and attach to the host plant with the help of suction cups – haustorium formed in places of contact with the feeding plant and deeply embedded in its tissue. The extraction of nutrients occurs due to the higher osmotic pressure of the parasite’s cell juice.

The stalk of the dodder is covered with numerous rather small, sessile or short-peduncle flowers with a double pericarp of white, pinkish or greenish color, collected in glomerular, spike-like or spherical inflorescences. The fruit is a box with four, rarely two or one spherical, oval or slightly elongated (sometimes irregularly shaped) seeds; on the inside, they are angular, covered with a solid cellular, pitted-rough shell.

Dodgers parasitize on annual and perennial grasses, shrubs and trees (fodder legumes, industrial, vegetable, melons, ornamental crops, vineyards, fruit trees, berry plants, wild grasses, shrubs and tree species). In addition to the main host plants, certain species of dodder can infect very many plants belonging to diverse families. Only a few species are specialized for certain nourishing plants.

Sucking water with organic and inorganic compounds dissolved in it, grafts cause metabolic disorders in host plants, weaken and delay their growth and development. Rapidly growing, the parasite covers entire arrays of susceptible culture, often causing the death of affected plants. Not only the yield is reduced, but also the winter hardiness of plants and the quality of the products is deteriorating. Grass cut by hay, infected with dodder, does not dry well, mold, lose its nutritional value, can cause animal diseases, and sometimes their death. Dodger also serves as a carrier of viral diseases of plants.

The spread of these flowering parasites occurs mainly with seeds of cultivated plants with poor cleaning. In addition, they are carried by animals, cars, water, wind; they fall into fields with manure if plants infected with dodder are fed to cattle; distributed with planting material, packaging. Wild plants and weeds infected with this parasite can serve as a source of infection.

The distinctive features of different species of dodder are the morphology of the stem and flowers, as well as specialization in parasitization on certain nourishing plants.

At dodder thyme thin yellowish or reddish thread-like stems branching thickness up to 1 mm, developing mainly in the lower part of the stems of the host plant, often forming a thick felt to the ground. The flowers are pink-white on very short peduncles, collected in dense spherical bundles. Fruiting is plentiful. It infects clover, alfalfa, vetch, beetroot, flax, potatoes, timothy, and many weeds.

The field crop has threadlike pale yellow branching stems that develop in the middle and upper parts of the affected plants. The flowers are white. Fruiting is plentiful. It infects tobacco, shag, beets, clover, vetch, alfalfa, lentils, peas, soy, cabbage, carrots, watermelon, pumpkin, potatoes, yellow clover, and many weeds.

At the alfalfa or close-up dodder, the stems are hairy-thin, yellow with a pink tint or greenish, smooth, glabrous, white flowers, gathered in dense glomeruli with bracts at the base. Fruiting is plentiful. Strongly affects alfalfa and many herbaceous plants.

Clover has threadlike, up to 1 mm thick, branched red stems. Before flowering, it spreads in the lower part of the stem of the feeding plant, where it forms a dense felt of branches, and only later rises above. The flowers are pink, less often – white, on very short pedicels, collected in dense spherical bundles. Parasitizes on clover, alfalfa, nick, beets, flax, potatoes and a number of weeds.

Flax flax has a greenish-yellow, medium thickness, juicy, unbranched stems. A cup of yellowish flowers is almost equal in length to the corolla. Seeds are single or double. Infects flax, camelina, clover, alfalfa, hemp, beets, and other cultivated and weed plants.

European dowel is similar to thyme dowry, from which it differs by a thicker (2.5 mm) reddish stalk. Her flowers are pinkish. Seeds are spherical or pear-shaped. It infects alfalfa, clover, sainfoin, hemp, beans, tobacco, hops, potatoes, lupins, testes of vegetable crops, numerous weeds, as well as shrubs and trees.

The single -stalk dodger has cord-shaped branched stems 2 mm thick or more. Her flowers are sessile or on short pedicels, collected in loose spike-shaped inflorescences. Corolla tube short, not protruding from the cup. Parasitizes on grapes, tree and shrub species can infect sunflower, cotton, beets, as well as some weeds (nettle, wormwood, quinoa).

Fodder fruits (capsules) contain from 2 to 5 small, 1-3 mm in diameter seeds, covered with a hard shell with a cellular, pitted, rough surface.

The germ in the dodder is not differentiated into cotyledons, the root and stem are a spirally twisted thread immersed in a gelatinous protein nutrient mass.